1. Field of the Invention
The present invention relates to an improvement of a clutch releasing bearing apparatus for vehicles, and more specifically, it relates to a clutch releasing bearing apparatus in which a portion of the apparatus against which an operating fork is abutted can be prevented from wearing due to contact or abutment therebetween.
2. Related Background Art
As is known, a clutch releasing bearing apparatus is axially shiftable and is arranged between a diaphragm of a clutch device and an operating fork operatively connected to a clutch pedal, and in such a manner that it is axially shifted by an operating force from the operating fork to transmit the operating force to the diaphragm, thereby releasing the clutch. In this arrangement, the operating fork contacts with or abuts against a portion of the clutch releasing bearing apparatus, and the transmission of the operating force to the diaphragm is normally effected by applying a mechanical force to the bearing apparatus from the operating fork through the contacted portions therebetween. However, in this case, the contacting portion of the bearing apparatus against which the operating fork is abutted is subjected to wear due to repeated clutch operations, thus increasing the "step-into" force or stroke of the clutch and/or impairing the release of the clutch.
According to one technique proposed to solve this problem, and as shown in FIG. 5, a rolling member 114 is interposed between the fork 110 and the bearing apparatus 112 to reduce the wear of the contacting portion of the bearing apparatus by rotation of the rolling member itself. This technique has been adopted, for example, as described in the U. K. Patent No. 1,495,775.
However, this conventional clutch releasing bearing apparatus has the following disadvantages. That is to say, since the fork 110 is rotated around a pin 116 on which the fork 110 is rotatably pivoted, the rolling member 114 is subjected to a force F from the fork 110 in a direction inclined by an angle .alpha. with respect to a central axis X--X' of the bearing apparatus (the direction of F being indicated by an arrow in FIG. 5). As a result, the rolling member 114 is radially lifted by the force F, thus applying a moment to the whole bearing apparatus via a holder 118 for holding the rolling member. Consequently, there arises a disadvantage that sliding resistance in sliding portions between the bearing apparatus 112 and a guide shaft 120 for guiding the bearing is increased, and, particularly in case of an aluminum guide shaft, jamming and/or abnormal abrasion will occur in the sliding portions due to deflection of those portions generated by the above-mentioned moment. Further, there is a problem that the repeated operation of the fork will cause wear of an inner guide surface for guiding the rolling member of the holder 118 and/or fatigue damage of a fixed portion of the holder stationary with respect to the bearing.
Another conventional clutch releasing bearing apparatus is taught by the Japanese Patent Laid-Open No. 62 - 242132. In this conventional apparatus, a bearing holding member (anvil) is provided at a surface thereof with a pair of diametrically opposed bearing receiving portions into which slide bearings each comprising a needle roller and a holder therefore are received, respectively. Each of the abutment plates comprises a rectangular plate incorporated into each of the slide bearings.
However, with this arrangement, this conventional apparatus has a disadvantage that the apparatus requires a large number of parts, is expensive, and is difficult to assemble. Further, there is a problem that, in use, the slide bearings and the abutment plates are easily inclined, thus preventing the rotation of the rolling members, and, thereby, considerably reducing any advantage obtained by the utilization of the rolling members.